I received several emails saying if I filed by 2/28 I would receive up to $30 off "Act Fast to Save up to $30 and Keep More of Your Cash". How do I use this and when?

I do not have a form 1098 to complete mortgage details. I went to lender's site to get my interest/taxes. The only field left is an empty check box that says, "Box 7 is checked". What does this mean???